After the 2012 London Olympics, Michael Phelps retired as one of the most decorated athletes in history. But was he truly done? He claimed so at the time, and has reaffirmed so repeatedly since, but more recent events suggest that maybe the door isn't entirely closed.

Last year, Phelps rejoined a drug-testing pool required for international competition, and he continues to work out regularly in Baltimore. The nine-month waiting period for drug testing has expired, meaning he is now free to compete at any time. His longtime coach Bob Bowman says that Phelps could return to competition "sometime soon."

Major events on the horizon include the U.S. championships this August and the world championships next year in Russia. Regardless of whether he competes in either or both of those, he could still seek to qualify for the 2016 Olympics in Rio. Bowman believes that Phelps would likely angle for shorter events such as the 100-meter butterfly and 100-meter freestyle.